The present invention relates to improvements in arrangements for damping torsional vibrations, especially for use in the power trains of motor vehicles, and more particularly to improvements in torsional vibration dampers of the type wherein at least two coaxial components, e.g., two flywheels, are rotatable with and relative to each other against the opposition or resistance of one or more resilient elements, such as coil springs. Still more particularly, the instant invention relates to improvements in torsional vibration dampers (hereinafter also called dampers for short) of the character wherein at least one of the components defines one or more chambers or compartments for one or more preferably arcuate coil springs each of which bears upon a first retainer provided on one of the components and reacts against a second retainer provided on another component. At least that surface or those surfaces which surrounds or surround the chamber or chambers radially outwardly of and lengthwise of the coil spring(s) serves or serve to limit the extent of movement of the coil spring or springs, e.g., under the action of centrifugal force.
Torsional vibration dampers of the above outlined character are disclosed, for example, in published German patent applications Nos. 4 117 582, 4 214 655, 4 414 584, 4 420 927 and 195 22 718.
Reference may also be had to commonly owned copending patent application Ser. No. 10/094,503 filed Mar. 8, 2002 by Johann Jackel et al. for xe2x80x9cTorsional Vibration Damperxe2x80x9d.
An object of our invention is to provide a torsional vibration damper which is more reliable, simpler and more effective than heretofore known torsional vibration dampers.
Another object of the present invention is to provide a torsional vibration damper which is less expensive than heretofore known dampers.
A further object of this invention is to provide a torsional vibration damper which can be assembled and installed, e.g., in the power train of a motor vehicle, in a simple and time-saving manner.
An additional object of the instant invention is to provide a torsional vibration damper with one or more coil springs or analogous energy storing units or assemblies which can perform their intended functions in an optimal manner not only at relatively low but also at higher and very high rotational speeds of the damper.
Still another object of the invention is to provide novel and improved energy storing means, particularly for use in torsional vibration dampers of the above outlined character.
A further object of the invention is to provide a novel and improved method of reducing or eliminating friction between the housing and the energy storing means in a torsional vibration damper of the above outlined character.
Another object of the present invention is to provide a power train which can be utilized with advantage in motor vehicles and which employs one or more torsional vibration dampers of the above outlined character.
An additional object of our invention is to provide a novel and improved combination of a torsional vibration damper and a friction clutch, particularly for use between the prime mover and the change-speed transmission in the power train of a motor vehicle.
Our invention resides in the provision of a torsional vibration damper which comprises a first component which is rotatable (e.g., by the prime mover in the power train of a motor vehicle) about a predetermined axis, and a second component which is rotatable about the predetermined axis with and relative to the first component. At least one of the components defines an arcuate chamber which is bounded by an internal surface of the at least one component, and the improved damper further comprises at least one energy storing unit which includes an elongated coil spring disposed in the arcuate chamber and serving to oppose rotation of the components relative to each other. The coil spring has a plurality of convolutions, a first end which bears upon a retainer of the first component (either directly or indirectly), a second end which reacts (directly or indirectly) against a retainer of the second component, and an intermediate portion between its ends. The at least one component includes a wall having an inner surface which forms part of the internal surface, which is disposed radially outwardly of the at least one coil spring and which extends circumferentially of the coil spring at least between the aforementioned ends of such spring. The damper further comprises friction reducing means including at least one slide which is interposed between the inner surface of the wall and the coil spring. The slide has an outer side which is adjacent the inner surface of the wall and the slide overlies at least one convolution of the coil spring. A radially outermost portion of the at least one convolution (namely the portion which is nearest to the inner surface of the wall) is engaged by at least one portion of the slide in such a way that the connection (a) prevents movements of the slide and the at least one convolution relative to each other longitudinally of the coil spring and (b) opposes movements of the slide and the at least one convolution relative to each other at least substantially radially of the common axis of the first and second components.
The components of the improved torsional vibration damper can form part of the power train in a motor vehicle. For example, one of the components can be rotated by the output shaft of an internal combustion engine, and the other component can serve to rotate the input shaft of a change-speed transmission in response to engagement of the friction clutch.
The at least one portion of the slide can be in form-locking and/or in force-locking engagement with a part of the outermost portion of the aforementioned at least one convolution of the coil spring.
The engagement between the slide and the at least one convolution of the coil spring can serve to oppose or prevent movements of these parts relative to each other only radially of the common axis of the components or only lengthwise of the coil spring.
It is often advisable to establish between the slide and the coil spring a connection which gives the at least one convolution of the spring limited freedom of pivotal movement with respect to the aforementioned at least one portion of the slide. For example, the extent of such pivotal movement can be in the range of between about 2xc2x0 and 10xc2x0.
In many or most instances, the convolutions of the coil spring consist of round wire, and the aforementioned portion of the slide can partially surround as well as extend lengthwise of the wire of the at least one convolution of the coil spring. The arrangement can be such that a median part of the aforementioned portion of the slide contacts the wire without any play or without appreciable play and two outer parts of such portion of the slide surround the wire with clearances or plays which increase in directions lengthwise of the wire and away from the median part.
The slide can further comprise at least one extension which projects from the at least one portion of the slide and lengthwise of the coil spring. It is presently preferred to design the slide in such a way that it comprises two extensions which flank the at least one portion of the slide and extend lengthwise of the coil spring toward the respective ends of the latter. Each extension can have an at least substantially wedge-shaped cross-sectional outline and the cross-sectional area of each extension preferably decreases with increasing distance from the at least one portion of the slide.
The entire slide can be made of a single piece of a suitable material, e.g., a plastic material. Alternatively, the slide can include a main part and the at least one portion of the slide can include or constitute a separately produced second part which is affixed to the main part. The second part can be at least substantially U-shaped and can include two resilient legs which clamp the outermost portion of the at least one convolution of the coil spring. The second part of the slide can consist, either in part or entirely, of spring steel. It is often preferred to design the second part in such a way that it can be secured to the at least one convolution of the coil spring by snap action.
The slide can have an arcuate shape and can overlie one, two or more neighboring convolutions of the coil spring. In a cross-sectional view, the slide can be U-shaped and can overlie one or more convolutions along an arc of 90xc2x0 or more, e.g., along an arc of at least 180xc2x0.
The coil spring can extend along an arc of at least 90xc2x0, e.g., it can occupy at least one fourth of the annular chamber. Furthermore, the friction reducing means can include a plurality of discrete slides.
The components of the improved torsional vibration damper can constitute discrete flywheels of a composite flywheel. As already mentioned hereinbefore, one of the components can normally receive torque from the prime mover of a motor vehicle and the other component can transmit torque to the input element (such as a shaft) of a change-speed transmission in the power train of the motor vehicle.
The aforementioned chamber can constitute a circumferentially complete annular chamber, and the damper can comprise at least one second energy storing unit in the chamber. Each unit can comprise several coil springs which are disposed end-to-end (i.e., in series) or a pair of interfitted coil springs (i.e., a smaller-diameter coil spring fitted into a larger-diameter coil spring.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved torsional vibration damping arrangement itself, however, both as to its construction and the modes of assembling, installing and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.